1. Field of the Invention
The present invention relates to an information recording medium, which includes bitmap information indicating whether each area has already been recorded or has not been recorded yet and on which a random write operation can be performed, and also relates to a method and apparatus for reading and/or writing from/to such a recording medium. The present invention is applicable particularly effectively to a write-once optical disc such as a high-density BD-R on which a write operation can be performed only once and to reading and writing from/on such a disc.
2. Description of the Related Art
Recently, various removable information storage media with huge storage capacities and disc drives for handling such media have become immensely popular. Examples of known removable information storage media with big storage capacities include optical discs such as DVDs and Blu-ray Discs (which will also be referred to herein as “BDs”). An optical disc drive performs a read/write operation by making tiny pits (or marks) on a given optical disc using a laser beam, and therefore, can be used effectively to handle such removable information storage media with huge storage capacities. Specifically, a red laser beam is used for DVDs, while a blue laser beam, having a shorter wavelength than the red laser beam, is used for BDs, thereby making the storage density and storage capacity of BDs higher and greater than those of DVDs. As for a BD-R, for example, a maximum storage capacity of as much as 27 gigabytes per recording layer has been realized.
For example, there is an optical disc that uses a phase change type recording material for its recording layer. A phase change type optical disc is irradiated with a laser beam and the atomic bonding state of a thin-film substance, which has been deposited on its recording layer, is locally varied with the energy injected, thereby writing information there. Also, when irradiated with a laser beam with much lower power than the one used for recording, the optical disc has its reflectance varied due to such a difference in physical condition. And if the magnitude of such a variation in reflectance is detected, the information stored there can be read out.
Phase change type optical discs include rewritable optical discs, on which information can be rewritten a number of times by using a phase change type recording material for its recording layer, and write-once optical discs, on which information can be written only once. If a mark edge write operation is performed on such a write-once optical disc, the disc is irradiated with a laser beam that has been modulated into a multi-pulse train to vary the physical condition of the recording material, thereby leaving recording marks there. And information is read out from such a write-once optical disc by sensing a variation in reflectance between those marks and spaces formed.
However, as an optical disc is a removable information recording medium, probably there will be some defect on its recording layer due to the presence of dust or a scratch. Among other things, the higher the density of a recording medium, the more easily the recording medium will be affected by defects. That is why it has become a more and more common measure to take to carry out a defect management on not just rewritable optical discs (such as a BD-RE) but also write-once optical discs (such as a BD-R) as well to ensure the reliability of the data read or written (see Patent Document No. 1 (Japanese Patent Application Laid-Open Publication No. 2005-56542), for example). Furthermore, a BD-R is characterized by having not only a sequential recording mode in which a write operation is carried out sequentially from a particular recording start point, as is typical of write-once storage media, but also a random recording mode as well, in which a write operation is performed on an arbitrary recording point (see Patent Document No. 2 (Japanese Patent Publication No. 3861856), No. 3 (U.S. Pat. No. 7,188,271) and #4 (United States Patent Application Publication No. 2007/0122124), for example).
FIG. 1 illustrates a normal layout of various areas on an optical disc. The disklike optical disc 1 has a spiral track 2, along which a great many subdivided blocks 3 are arranged. Blocks 3 are not only units of error correction but also the smallest units of read/write operations. Each block 3 is called sometimes a “cluster” as for BDs and sometimes an “ECC” as for DVDs. One cluster, which constitutes one block for a BD, is equal to 32 sectors (i.e., one sector has a size of 2 kilobytes and one cluster has a size of 64 kilobytes). On the other hand, one FCC, which constitutes one block for a DVD, is equal to 16 sectors (i.e., 32 kilobytes). Also, the storage area on the optical disc 1 is roughly classified into a lead-in area 4, a data area 5 and a lead-out area 6. User data is supposed to be read from, and written on, the data area 5. The lead-in area 4 and the lead-out area 6 function as margins that allow the optical head (not shown) to get back on tracks even if the optical head has overrun while accessing an end portion of the data area 5. That is to say, these areas 4 and 6 function as “rims” so to speak. Such a layout of areas is used commonly on both a rewritable optical disc and a write-once optical disc.
FIG. 2 shows the data structure of a single recording layer of a conventional write-once optical disc with a defect management function.
The data area 5 is made up of a user data area 14, from/on which user data is read or written, and spare areas, each of which is defined in advance to provide an alternative block (which will be referred to herein as a “replacement block”) for a defective block, if any, in the user data area 14. In the example illustrated in FIG. 2, an inner spare area 15 is arranged closer to the inner edge of the optical disc 1, and an outer spare area 16 is arranged closer to its outer edge. That is to say, although one spare area is arranged inside of the data area 5 and another spare area is arranged outside of the data area 5 in FIG. 2, the spare area could be provided on only one of these two sides (e.g., only inside of the data area 5). Therefore, the arrangement shown in FIG. 2 does not always have to be adopted.
Each of the lead-in and lead-out areas 4 and 6 has areas to store a disc management structure (which will be abbreviated herein as “DMS”) that provides pieces of management information about the arrangement (or size) of the spare areas on the optical disc 1, the recording mode, defective blocks and so on. Specifically, the lead-in area 4 includes first and second disc management areas (DMAs) 10 and 11 (which will be referred to herein as “DMA #1” and “DMA #2”, respectively). On the other hand, the lead-out area 6 includes third and fourth DMAs 12 and 13 (which will be referred to herein as “DMA #3” and “DMA #4”, respectively). It should be noted that DMA sometimes stands for a defect management area.
DMA #1 through #4 are arranged in their own areas and store quite the same pieces of management information except some predetermined kind of information such as location information, which is done to prepare for a situation where any of the DMA #1 through #4 has gone defective itself. That is to say, even if information can no longer be retrieved from one of these four DMAs properly, the defect management information can still be acquired as long as there is at least one DMA from which information can be retrieved properly.
The lead-in area 4 further has a first TDMA (temporary disc management area) 17. The TDMA is an area unique to a write-once optical disc which is a non-rewritable (i.e., non-updatable) disc and is used to add temporary management information and update it while the optical disc 1 is being used. It should be noted that TDMA sometimes stands for a temporary defect management area.
Hereinafter, it will be described with reference to FIG. 14 exactly how to use the TDMA 17. First of all, initialization formatting processing (which is also called simply “initialization”) is carried out so that the write-once optical disc 1 gets ready to be used by determining the arrangement (or size) of the spare areas and the recording mode, thereby recording initial TDMS (temporary disc management structure) 20 as shown in portion (a) of FIG. 14.
Next, as shown in portion (b) of FIG. 14, write processing is performed on the user data area 14 and TDMS #0 21, of which the information (such as defect information and recording end point information) has been updated as a result of the write processing, is written at the top of the unrecorded area of the TDMA 17 (i.e., so as to consume the unrecorded area to the right from the boundary between the recorded area and the unrecorded area).
After that, the management information will be updated in the same way a number of times. And portion (c) of FIG. 14 illustrates a state in which the management information has been updated (m+1) times since the initialization formatting processing was done. That is to say, the latest piece of management information (i.e., the latest TDMS) will be the recorded TDMS (i.e., TDMS #m 21 in FIG. 14) that is adjacent to the boundary between the recorded and unrecorded areas of the TDMA 17.
The arrangement of the DMAs is not different between a write-once optical disc and a rewritable optical disc. However, since the rewritable optical disc is rewritable (i.e., updatable), every piece of management information, including the temporary management information while the optical disc 1 is being used, can be updated in these DMA areas. On the other hand, the write-once optical disc is not rewritable (i.e., non-updatable). That is why the write-once optical disc 1 has an area called “TDMA” for updating temporary information, which cannot be found in any disc other than write-once ones. And when finalize (also called “disc close”) processing is carried out to prohibit the user from newly adding any further piece of information to the optical disc 1 and make the disc a read-only one, the contents of the latest TDMS are copied onto the DMA.
In the example illustrated in FIG. 2, only one TDMA 17 is supposed to be arranged in the lead-in area 4. However, two or more TDMAs 17 could be arranged (see Patent Document No. 5 (Japanese Patent Publication No. 3865261, for example). Optionally, multiple TDMAs may also be provided for each recording layer and arranged in the spare areas, too. For instance, as shown in FIG. 15, additional TDMA #1 and TDMA#2 may be respectively provided for the inner and outer spare areas 15 and 16 of the data area 5, in addition to TDMA #0 in the lead-in area 4. Also, if the write-once optical disc 1 has multiple recording layers, those TDMA areas may be provided for each of those multiple recording layers.
The DMS written on the DMAs and the TDMS 21 written on the TDMA 17 are both made up of the same elements. In the following description, the TDMS 21 will be described as an example.
FIG. 16 illustrates elements that form a TDMS 21 on a BD-R, which is a write-once optical disc, in the random recording mode. In FIG. 16, the structure of a write-once optical disc 1 with only one recording layer is shown as an example. That is why the data that each of these pieces of information contains is supposed to be provided for just one recording layer in the example illustrated in FIG. 16.
The TDMS 21 consists of an SBM (space bitmap) 30, a TDFL (temporary defect list) 31 and TDDS (temporary disc definition structure) 32.
The SBM 30 has an SBM header 40 including an identifier disclosing its identify as the SBM 30, information about the number of times of update, and information about the range of the SBM area to manage (e.g., the top address and size of the area in question), and bitmap information 41 indicating the recording statuses (e.g., recorded and unrecorded states) in that range of the SBM area to manage. The bitmap information 41 will be described in further detail later. In an optical disc 1 with multiple recording layers, the data areas 5 on which the SBM 30 can be managed (more specifically, the user data area 14) are not physically continuous with each other between its multiple recording layers, and therefore, the SBM 30 is provided for each of those recording layers.
The TDFL 31 has: a DFL header 42 including an identifier disclosing its identity as the TDFL, information about the number of times of update, and information about the number of DFL entries 43 (e.g., n+1 in FIG. 16), which is defect and replacement information of the TDFL; that number of DFL entries 43; and a DFL terminator 44 including an identifier disclosing its identity as the terminal position of the TDFL 31, of which the size is variable according to the number of DFL entries 43, and information about the number of times of update. The TDFL 31 and the TDDS 32 of one sector size (to be described later) may have a size of at most four blocks (i.e., four clusters as for a BD) combined if there is only one recording layer and may have a size of at most eight blocks (i.e., eight clusters as for a BD) combined if there are two recording layers. That is to say, the size of the TDFL 31 itself is supposed to be at most “four blocks (i.e., four clusters as for a BD) minus one sector” if there is only one recording layer but at most “eight blocks (i.e., eight clusters as for a BD) minus one sector” if there are two recording layers.
The TDDS 32 has: a DDS header 50 including an identifier disclosing its identity as the TDDS 32 and information about the number of times of update; an inner spare area size 51 and an outer spare area size 52, which are pieces of information about the respective sizes of the inner and outer spare areas 15 and 16 that determine the layout of the respective areas in the data area 5; recording mode information 53 indicating whether the recording mode is sequential recording mode or random recording mode; inner spare area TDMA size 54 and an outer spare area TDMA size 55 providing size information in a situation where there are TDMAs in the inner and outer spare areas 15 and 16 as shown in FIG. 15; SBM #0 location information 56, which is information about the storage location of the latest SBM 30; and DFL #0 location information 57, DFL #1 location information 58, DFL #2 location information 59, and DFL #3 location information 60, which are pieces of location information of the respective blocks in which the latest TDFL 31 (of at most four blocks) is stored.
The TDDS 32 has a fixed size, e.g., a size of one sector as described above.
Hereinafter, the bitmap information 41 will be described in detail with reference to FIG. 19. The bitmap information 41 is a piece of information for use to check recorded and unrecorded portions of a data area on a block-by-block basis, for example. In the bitmap information 41, one block of a given area range, of which the SBM needs to be managed (e.g., the user data area 14), is associated with one bit, the status of that block is indicated to be zero if it is still an unrecorded block, but its status is changed into one when the block turns into a recorded one. That is to say, supposing the eight blocks A through H in the given area range, of which the SBM needs to be managed, get associated with bits 0 through 7, respectively, in the one-byte (i.e., eight-bit) data at a predetermined byte position in the bitmap information 41 as shown in FIG. 19, if the entire area of interest is unrecorded as shown in FIG. 19(A), every bit (i.e., from bit 0 through bit 7) of the bitmap information 41 will be zero. On the other hand, after a write operation has been performed on the blocks B, C and F, their associated bits 1, 2 and 5 of the bitmap information 41 will become one and the one-byte (i.e., eight-bit) data at the predetermined byte position of the bitmap information 41 will be 26h, which is a hexadecimal number as shown in FIG. 19(B). Since one block is associated with one bit, 4000h (which is a hexadecimal, too) blocks can be managed using one sector (2 kilobytes) of bitmap information 41 and 78000h (which is also a hexadecimal and which is 491,520 according to decimal notation) blocks can be managed using 30 sectors of bitmap information 41.
As for a BD-R, if the maximum capacity per recording layer is 27 gigabytes, the maximum number of blocks (or clusters) included in the user data area 14 is less than 68000h (which is again a hexadecimal). That is why it should be enough if the bitmap information 41 has a size of 30 sectors. As a result, supposing the SBM header 40 has a size of one sector, it is possible to ensure that the combined size of the SBM 30 with a size of 31 sectors and the TDDS 32 with a size of one sector is always equal to or smaller than one block (i.e., 32 sectors or one cluster). On the other hand, as the size of the TDFL 31 is variable according to the number of DFL entries 43, it is impossible to ensure that the combined size of the TDFL 31 and the TDDS 32 is always equal to or smaller than one block.
Each of the SBM 30 and the TDFL 31 is always written on the TDMA 17 using its combination with the TDDS 32 as a single recording unit (which is called a “disc management structure update unit”).
Next, the initial TOMS 20 (see FIG. 14) will be described.
The initial TDMS 20 is arranged at the top of the TDMA 17 (i.e., at the position to be used (recorded) earliest on the optical disc 1).
The initial TDMS 20 has the same elements as, but slightly different contents from, a normal TDMS 21. As shown in FIG. 17, the initial TDMS 20 includes one block (i.e., one cluster) of data as a combination of the initial SBM 30 and the TDDS 32 that form one disc management structure update unit, and another block (i.e., another cluster) of data as a combination of the initial TDFL 31 and the TDDS 32 that form another disc management structure update unit.
As used herein, the “initial SBM 30” refers to an SBM, for which only information about the identifier of its SBM header 40 and the area range of the SBM to be managed are defined and information about the number of times of its updates and the bitmap information 41 are all zero (i.e., the user data area 14 is totally unrecorded).
Also, the TDDS 32 to be written in combination with the initial SBM 30 not just includes the DDS header 50 providing only identifier information but also defines the sizes of the respective spare areas (i.e., the inner and outer spare area sizes 51 and 52), the sizes of the TDMAs in those spare areas (i.e., inner- and outer-spare-area TDMA sizes 54 and 55) and recording mode information 53 (e.g., random recording mode in this example). Furthermore, information about the location at which the SBM 30 is going to be written is stored as the SBM #0 location information 56. DFL #0 location information 57 corresponding to the initial TDFL 31 to be described later is stored as the TDFL location information, and indicates the block location on which the initial TDFL 31 and TDDS 32 are written next to the initial SBM 30 and the TDDS 32.
As for the DFL #1, #2 and #3 location information 58, 59 and 60 not to be used, null data (e.g., zero) indicating that these pieces of information are not available may be written, for example.
Also, the initial TDFL 31 refers to a TDFL of the minimum size including no DFL entries 43 at all, i.e., the TDFL includes only the DFL header 42 (which provides only identifier information, but of which the number of DFL entries 43 and information about the number of times of updates are both zero) and the DFL terminator 44 (for which identifier information has been defined but of which the number of times of update information is zero). Since the initial TDFL 31 has a size that is equal to or smaller than one sector size, the combined size will be equal to or smaller than one block (or cluster) size even when written in combination with the TDDS 32. Furthermore, the TDDS 32 to be written in this case may have almost the same data as what is written as the initial SBM 30 and TDDS 32 described above. It is only the DFL #0 location information 57 that can be different. That is to say, if data cannot be written on an intended block due to the presence of a defect, for example, but has been written on the next block instead, for example, only this value can be different from the value of the TDDS 32 that has been written with the initial SBM 30.
As described above, at the top of the TDMA 17, stored is a portion of the data of the initial TDMS 20. In addition, at that top location, always written is a TDDS 32 that provides information that clearly indicates the area arrangement and recording mode of the data area 5 on the optical disc 1. Thus, even if it is impossible to decide, on the spot, exactly where such a TDDS 32, providing information that indicates the area arrangement and recording mode of the data area 5 on the optical disc 1, is located (e.g., if there are a number of TDMAs or if the TDMA has already been updated a number of times), the area arrangement and recording mode of the data area 5 can still be determined definitely by reading out the data from one block at the top of the TDMA 17 (or the first one of its following blocks on which a read/write operation can be performed properly if it is a defective block).
Particularly, in a situation where a read-only apparatus for the optical disc 1 is loaded with an optical disc 1 with no spare areas, as long as at least the layout (i.e., area arrangement) of the optical disc 1 is known, that apparatus can also perform read processing at the read request issued by the host even without getting the latest management information. That is why the latest management information is not always required and the TDDS 32 indicating the layout of the optical disc 1 is preferably obtained as soon as possible and as securely as possible. Therefore, from that standpoint, it is also preferred that data that always has the TDDS 32 at a predetermined location (e.g., one block at the top of the TDMA 17) be written.
Furthermore, in a situation where there are multiple TDMAs, if the size information of the TDMA located on the spare area were not available, then even the location of that TDMA could not be determined. For that reason, it is very important and efficient for an optical disc drive to perform a read/write operation on this optical disc 1 that the data of the TDDS 32 is always arranged at a predetermined location (e.g., at the top of the TDMA 17 in this example).
In the foregoing example, a random recording mode has been described. In a sequential recording mode, on the other hand, SRRI (SRR information), providing information about the top location of recording tracks (which are also called an SRR (sequential recording range)) and information about the end location of the recorded portion, will just be written instead of the SBM 30. In that case, the initial TDMS consists of an initial TDFL 31, an initial SRRI and a TDDS 32, has a size that is equal to or smaller than one block (or one cluster) and therefore, written as one block (one cluster) data.
It should be noted that a DMS to be written on a DMA and a TDMS to be written on a TDMA have mutually different orders of data written and arranged. Specifically, in the TDMS, the TDDS is arranged at the end of the TDMS. In the DMS, on the other hand, the DDS is arranged at the top location of the DMS (see Patent Document No. 1 (Japanese Patent Publication No. 2005-56542).
Also, recently, people have been trying harder and harder to further increase the storage capacities of optical discs. Examples of those methods for realizing optical discs with huge capacities (i.e., methods for increasing their storage capacities) include increasing the storage density per recording layer by shorting the lengths of recording marks and spaces to be left or shortening the track pitch and increasing the overall storage capacity by providing multiple information recording layers.
Among these methods, according to the method for increasing the storage density per recording layer by shortening the lengths of the marks and spaces to be left, a storage density of 32 gigabytes or 33.4 gigabytes per recording layer, which is approximately 25% greater than the maximum size of 27 GB of conventional BDs, is expected to be realized. And even higher storage densities could be realized in the future, too.